Infrared transceivers modules are often incorporated into electronic devices to enable bi-directional wireless communication with other electronic devices. For example, it is known for a portable digital assistant (PDA) to communicate with a laptop computer, a printer, or another PDA via a standard Infrared Data Association (IrDA) link. Similarly, IR transceivers are becoming increasingly popular for use in hand-portable telephones, enabling telephone users to swap stored numbers, play wirelessly-linked games, or wirelessly link their telephones to IR-enabled accessories. Other devices which have IR transceivers include, for example, pagers, digital cameras, printers and personal computers.
The advantages of using an IR link over standard electrical connectors are numerous and well documented. These advantages include: 1) greater alignment tolerance; 2) the ability to hermetically seal the data interface; 3) no cables susceptible to RF interference; and 4) no electromagnetic compatibility (EMC) issues.
An IR transceiver module typically comprises a light emitting diode (LED) and a photodiode, packaged together with appropriate supporting circuitry to form a self-contained unit. Electrical terminals are exposed on the outside of the package to enable the module to be electrically coupled to external circuitry.
By combining the various components of an IR transceiver into a single package or module, the size or form-factor of the transceiver system can be considerably reduced. Furthermore, the modules tend to be more durable and often consume less power than equivalent transceivers consisting of discrete components.
When an IR link or communication channel is created between two IR transceiver modules, the LED in the first transceiver optically couples with the photodiode in the second transceiver, and the LED in the second transceiver optically couples with the photodiode in the first transceiver. FIG. 1 illustrates two spaced apart devices 10, 20 which are communicating via such an IR link 30. Although the transceivers typically operate in the infrared optical frequency band it is equally possible for other optical frequency bands to be used in forming the communication channel 30.
FIG. 2 is an internal view of the device 10 of FIG. 1, showing the IR transceiver module 200 mounted on an end portion of a main printed circuit board (PCB) 250. The transceiver module 200 comprises a main body 240 including a first molded lens shape 210 over the LED and a second molded lens shape 220 over the photodiode. Leads 230 provide mounting supports and electrical interconnections between the IR transceiver 200 and the printed circuit board 250. A typical length for the IR transceiver body is approximately 10 mm, a typical depth is 5 mm, and a typical height is 4 mm.
It is known to include an ambient light detector in certain electronic devices to detect the ambient light conditions in the environment of the device. For example, the model CB-21Q20ET television available from LG Electronics, Korea includes a light detector which detects ambient light conditions so that the television picture contrast can be set appropriately.